The Role Of Axial Flow Fans And Centrifugal Fans in Grain Storage Ventilation

1. Due to the large difference between air temperature and grain temperature, the first ventilation time should be selected during the day to reduce the difference between grain temperature and air temperature and reduce the occurrence of condensation. The subsequent ventilation should be carried out at night as much as possible, because this ventilation is mainly for cooling. At night, the atmospheric humidity is relatively high and the temperature is low, which reduces water loss and makes full use of the low temperature at night to improve the cooling effect.
2. In the early stage of ventilation with centrifugal fans, condensation may occur on doors, windows, walls, and even slight condensation on the surface of grain. Just stop the fan, open the window, turn on the axial flow fan, and turn the grain surface when necessary to remove the hot and humid air in the warehouse. When using axial flow fans for slow ventilation, there will be no condensation, only the temperature of the middle and upper layers of grain will slowly drop, and the grain temperature will drop steadily as the ventilation continues.
3. When using axial flow fans for slow ventilation, due to the small air volume of axial flow fans and the fact that grain is a poor conductor of heat, it is easy to have slow ventilation in some parts at the beginning of ventilation. As the ventilation continues, the grain temperature of the whole warehouse will gradually balance.
4. The grains for slow ventilation must be cleaned by the vibrating screen, and the impurity area caused by automatic grading must be cleaned in time when entering the warehouse, otherwise it is easy to cause uneven local ventilation.
5. Energy consumption calculation: The axial flow fan in warehouse No. 14 was ventilated for a total of 50 days, an average of 15 hours a day, a total of 750 hours, the average moisture content dropped by 0.4%, the average grain temperature dropped by 23.1 degrees, and the unit energy consumption was: 0.027kw.h/t.℃. The 28th warehouse was ventilated for a total of 6 days, a total of 126 hours, the average moisture content dropped by 1.0%, the average temperature dropped by 20.3 degrees, and the unit energy consumption was: 0.038kw.h/t.℃.
6. Advantages of slow ventilation with axial flow fans: good cooling effect; low unit energy consumption, which is particularly important today when energy conservation is advocated; easy to grasp the ventilation timing, and condensation is not easy to occur; no separate fan is required, which is convenient and flexible. Disadvantages: Due to the small air volume, the ventilation time is long; the precipitation effect is not obvious, and high-moisture grain is not suitable for ventilation with axial flow fans.
7. Advantages of centrifugal fans: obvious cooling and precipitation effects, short ventilation time; Disadvantages: high unit energy consumption; condensation is easy to occur if the ventilation timing is not well grasped.
8. Conclusion: In ventilation for the purpose of cooling, axial flow fans are used for safe, efficient, and energy-saving slow-speed ventilation; centrifugal fans are used for ventilation for the purpose of precipitation.